As someone who saw the anime almost a decade ago, which was an adaptation of a manga by the same name, I was very curious how this story could possibly be adapted into live action without looking very silly (see the Japanese live adaptation films).
Without spoiling anything, The Grey is not another live-adaptation of the manga, nor is it a sequel to it. It's more like a spin-off. The events that happen in Parasyte, in the original material, we only saw what happened in Japan. The Grey looks at what happens when the parasytes affects a different country. In this sense, you don't have to read the manga or watch the anime, as the TV series cover the worldbuilding fairly well.
Now, the big question is, did it end up looking as silly as the films? No. I'd say the special effects in The Grey were awesome. Probably the best parts of the show. It will no doubt look a bit cartoonish still but I was very impressed. How much of it was practical effects? How much was it VFX? They have blended it very well.
However, the shaky cam definitely didn't do the show any favours. Maybe it was a necessary evil to make the VFX looks as real as it did, but I rather have the camera stationary so we can focus on the fights, because some of the fights were pretty insane. But again, it might be because the cuts and shaky cams hid a lot of glaring issues and is why it was used.
Still, Parasyte was and still is an interesting series just because it asks some interesting questions about humanity, survival, and morality. I don't think the philosophy was as in-depth as the manga or anime, given there were only 6 episodes, but there is enough to ponder here and definitely makes me want to watch the anime again (highly recommended but also has its fair share of flaws). For those who knew the source material, the last couple minutes in this show was super cool to see.
In summary, Parasyte has an interesting premise and the TV series did an excellent job adapting it as a live action. Slowly, I think Netflix is producing more and more quality live adaptations which had been known for a long time to be a joke (Cowboy Bebop and Death Note is still a joke but Alice in Wonderland and One Piece was very good).
